DAC

Set and read back an analog output voltage

Drive an analog output voltage into your DUT from a DAC net.

Handle

use lager::LagerBox;

let lager = LagerBox::from_env()?;
let dac = lager.dac("dac1");

Methods

Method	Description
name()	The net name this handle addresses
set()	Set the output voltage in volts
read()	Read back the current output voltage

Method Reference

name() -> &str

The net name this handle was created with.

set(volts: f64) -> Result<()>

Set the output voltage.

dac.set(1.8)?;

Parameters:

Parameter	Type	Description
volts	f64	Target output voltage in volts

read() -> Result<f64>

Read back the voltage that the DAC currently outputs.

let v = dac.read()?;

Returns: f64 — the output voltage in volts.

Not every DAC supports readback. On an MCC USB-202 this call fails with Error::Box and the message USB-202 does not support DAC output readback. A LabJack U3 has no readback either. The box returns the last value that it set, and the call fails when the box has no value. Where you need a verified output, measure it with an ADC net instead of trusting read() to exist.

Examples

Sweep a reference and check the DUT tracks it

let dac = lager.dac("dac1");
let sense = lager.adc("adc1");

for target in [0.0_f64, 0.5, 1.0, 1.5, 2.0] {
    dac.set(target)?;
    std::thread::sleep(std::time::Duration::from_millis(50));
    let measured = sense.read()?;
    assert!((measured - target).abs() < 0.05,
            "set {target:.2} V, measured {measured:.4} V");
}
dac.set(0.0)?;

Supported Hardware

Instrument	Channels	Readback
LabJack T7	DAC0, DAC1	Supported
LabJack U3	DAC0, DAC1	Last value that the box set; output range 0.04 V to 4.95 V
MCC USB-202	DAC0, DAC1	Not supported

Notes

• Leave the output where the next test expects it. A DAC holds its last value after your test ends; setting it back to 0.0 in teardown is usually right. A LabJack U3 refuses 0.0, because its range is 0.04 V to 4.95 V. On a U3, use 0.04.
• Output accuracy is the instrument’s, not the API’s. A LabJack T7 asked for 1.0 V reads back around 0.99995 V, which is the DAC’s resolution rather than an error.